A conventional internal combustion engine (ICE) having a piston cylinder attached to a crank arm or yoke offset from the crank shaft proceeds through various processes in a typical cycle; intake, compression, power, and exhaust. In a four stroke engine, each process occurs in each stroke of the piston, i.e., first stroke (downward) corresponds to an intake process or charging of a fuel-air mixture, second stroke (upward) corresponds to a compression process of the mixture, third stroke (downward) corresponds to a power process in which the mixture is ignited to produce energy for turning the crank, and fourth stroke (upward) corresponds to the exhaust process which vents the waste products of combustion from the piston chamber. The directions indicated above in parentheses are mainly illustrative of a configuration in which the piston cylinder is arranged to reciprocate in a vertical orientation. It is noted that many conventional ICEs include various configurations of pistons that depart from vertical.
Another common type of ICE is a two-stroke engine in which two of the four processes mentioned above occur in the same stroke. For example, the first stroke (downward) includes the intake and power processes while the second stroke (upward) includes the compression and exhaust processes.
The efficiency of the above mentioned engines is measured in part by how an engine maximizes the thermo energy produced via combustion, since an ICE is fundamentally a practical application of heat transfer thermodynamics. It is recognized that many factors are involved in determining the efficiency of an ICE, e.g. the crank and piston geometry, compression ratios, charge durations, burn durations, engine tuning parameters, air-fuel mixture, engine block temperature, etc. However, one of the main factors for inefficient operation in an engine is potential heat loss during a cycle. Some attributing examples may be mistimed ignition of the air-fuel mixture that results in less than maximum consumption of the resource and thereby produces sub-optimal power to turn the crank, or simple heat loss between the piston cylinder chamber and the surrounding engine block and/or other attached components. Hence, most commercial engines in vehicles have roughly 20% efficiency. Due to current economics and dwindling resources, there exists a need for more efficient engines.
International PCT application number US2009/06700 discloses a dwell cycle crank designed to solve the aforementioned problems. This international application in its entirety is incorporated herein by reference. The dwell cycle crank of said application includes a reciprocating piston having a piston head or cylinder, a main body connected to the piston head, a cap detachably mounted to the main body, an S-shaped cam formed between the main body and the cap, a connecting bearing or follower disposed in the S-shaped cam, a rotatable crankshaft, and an offset journal disposed between the connecting bearing and the crankshaft to thereby form a torque arm. FIGS. 1-3 of this application show the dwell cycle crank of this prior art PCT application. The S-shaped cam and connecting bearing create dwells and faster strokes at key points in the crank cycle to maximize volumetric and geometric efficiencies of the engine.
Although the dwell cycle crank of International PCT application number US2009/06700 is known to improve the volumetric and geometric efficiencies of the engine, this prior art dwell cycle crank can be improved. One area that could be improved was the heavy contact points between the follower and the top and bottom of the S-shaped cam. These heavy contact points may lead to wearing down of the follower and/or S-shaped cam which may lead to decreased performance and efficiency of the engine and/or engine failure. Thus, there is clearly a need to improve the dwell cycle crank of International PCT application number US2009/06700 by reducing or eliminating the heavy contact points between the follower and the S-shaped cam.
The instant invention is designed to provide a dwell cycle crank that addresses the above mentioned problems.